Our product incorporates your BC127 Bluetooth module as audio gateway for Iridium 9523 Voice Transceiver with PCM master clock 2048 kHz, and 8 kHz frame sync.
The Melody 6.1.5 version provides good audio quality but with issues controlling audio volume.
We have tried to upgrade to Melody 7.1 and 7.2 but the audio is unintelligible.
I have reproduced this unintelligible audio with Melody 7.2 on your Discovery Board.
The issue appears to be associated with Auto-adjust digital rate setting.
The Iridium 9523 operates only at 8 kHz (125 uSeconds) Voice Audio Rate.
Test Setup Using - BC127 Discovery Board v2 No Co Processor
Load Melody 7.2 into Discovery Board
Select PCM Audio - J6 Grounded (pin 2 to 3)
Jumper PCM_OUT to PCM_IN J4 (pin 3 to 4)
Configure Digital Audio - BC127 as PCM Master
Connect Bluetooth Headset
Establish Headset Audio Path
Configuration One: SET AUDIO_DIGITAL=1 8000 2048 2500020 ON
Observed Sync Rate (PCM_SYNC) - 62.5 uSeconds
Observed Clock Rate (PCM_CLK) - 2048 kHz
Audio Quality - Very Good
Configuration Two: SET AUDIO_DIGITAL=1 8000 2048 2500020 OFF
I have read the release notes for version 7.1 and 7.2 and expected them to behave consistent with version (6.1.5). Both Configuration One and Two with the exception of the last parameter enable_auto_rate (not implemented in 6.1.5); product good quality audio. The digital rate (2nd) parameter in the AUDIO_DIGITAL should define the frame sync rate for PCM audio. I also noticed that setting the 16000 rate produces an Error Code 0x0013 (wrong parameter).
So it seems to me that neither 6.1.5 or 7.2 firmware like the 16KHz frequency you are trying to send to it as they both return ERROR 0x0013.
6.1.5 firmware
version
BlueCreation Copyright 2017
Melody Audio V6.1.5
Build: 1496939390
Bluetooth address 20FABB075D3F
Profiles: A2DP AVRCP HFP BLE SPP PBAP MAP
Codecs: SBC
OK
SET AUDIO_DIGITAL=1 8000 2048 2500020
OK
SET AUDIO_DIGITAL=1 16000 2048 2500020
ERROR 0x0013
SET AUDIO_DIGITAL=1 8000 2048 2500020
OK
SET AUDIO_DIGITAL=1 16000 2048 2500020
ERROR 0x0013
7.2 firmware
version
Sierra Wireless Copyright 2018
Melody Audio V7.2
Build: 1534785311
Bluetooth addresses: 20FABB075D0B 5CF8AFC1D837
Profiles: A2DP AVRCP HFP BLE SPP PBAP MAP TWS
Codecs: SBC
OK
SET AUDIO_DIGITAL=1 8000 2048 2500020
OK
SET AUDIO_DIGITAL=1 8000 2048 2500020
OK
SET AUDIO_DIGITAL=1 16000 2048 2500020
ERROR 0x0013
SET AUDIO_DIGITAL=1 16000 2048 2500020
ERROR 0x0013
We do have an issue with the inability to independently control the incoming and outgoing volume level. The separation of volume control was to be implemented in Melody (7.2). We have been unable to produce usable audio with the new version code.